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• Naive Sorenson Video 1 Encoder

  12 septembre 2010, par Multimedia Mike — General

  (Yes, the word is “naive” — or rather, “naïve” — not “native”. People always try to correct me when I use the word. Indeed, it should actually be written with 2 dots over the ‘i’ but who has a keyboard that can easily do that ?)

  At the most primitive level, programming a video encoder is about writing out a sequence of bits that the corresponding video decoder will understand. It’s sort of like creating a program — represented as a stream of opcodes — that will run on a given microprocessor or virtual machine. In fact, reading a video codec bitstream specification will reveal a lot of terminology along the lines of “transmitting information to the decoder” or “signaling the decoder to do xyz.”

  Creating a good encoder that will deliver decent quality at a reasonable bitrate is difficult. Creating a naive encoder that produces a technically compliant bitstream, not so much.

  
  
  

  When I wrote an FFmpeg encoder for Sorenson Video 1 (SVQ1), the first step was to just create a minimally compliant bitstream. The coarsest encoding mode that SVQ1 allows is to encode the average (mean) of each 16×16 block of samples. So I created an encoder that just encoded the mean of each block. Apple’s QuickTime Player was able to play the resulting video in all of its blocky glory. The result rather reminds me of the Super Nintendo’s mosaic effect.

  Level 5 blocks (mean-only 16×16 encoding) :
  

  
  
  

  Level 3 blocks (mean-only 8×8 encoding) :
  

  
  
  

  It’s one thing for your own decoder (in this case, FFmpeg’s own decoder) to be able to decode the data. The big test is whether the official decoder (in this case, Apple QuickTime Player) can decode the file.

  
  
  

  Now that’s a good feeling. After establishing that sort of baseline, it’s possible to adapt more and more features of the codec.

• Merge commit ’b70d7a4ac72d23f3448f3b08b770fdf5f57de222’

  15 mai 2014, par Michael Niedermayer

  Merge commit ’b70d7a4ac72d23f3448f3b08b770fdf5f57de222’
  * commit ’b70d7a4ac72d23f3448f3b08b770fdf5f57de222’ :
  
    lavc : add a native Opus decoder.
  Conflicts :
  
  	Changelog
  
  	configure
  
  	libavcodec/version.h
  Fate tests pass with both avresample as well as swresample based opus decoder, but
  
  are disabled (reference files are very large so i want to think a day or 2 about
  
  if theres an alternative or if they could be avoided, they also dont match the
  
  official samples)
  Merged-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] Changelog
  • [DH] configure
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/allcodecs.c
  • [DH] libavcodec/opus.c
  • [DH] libavcodec/opus.h
  • [DH] libavcodec/opus_celt.c
  • [DH] libavcodec/opus_imdct.c
  • [DH] libavcodec/opus_parser.c
  • [DH] libavcodec/opus_silk.c
  • [DH] libavcodec/opusdec.c
  • [DH] libavcodec/version.h
  • [DH] tests/Makefile
  • [DH] tests/fate/opus.mak

• add libaribb24 ARIB STD-B24 caption decoder

  14 janvier 2019, par Jan Ekström

  add libaribb24 ARIB STD-B24 caption decoder
  * Outputs ASS lines with basic coloring and font scaling for each
  
    given region.
  
  * Sets the default style to the resolution of the subtitle plane
  
    (for example, 960x540 / 36pt font for profile A).
  
  * Has options to :
  
    * Disable ruby text (which is coded as regions which have
  
      half-height text in libaribb24).
  
      Enabled by default as without positioning ruby text only
  
      confuses as it is usually coded in the beginning of the decoded
  
      subtitle line.
  
    * Set the working directory, in which libaribb24 will read
  
      configuration as well as into which it may save broadcast extra
  
      symbols as PNG.
  
      Unset by default.
  The unconventional library check can be explained by the library's
  
  current master branch being licensed as LGPLv3, but at the time of
  
  writing the latest official release is still licensed under GPLv3.
  Thus, one either has to wait for the following release, or enable
  
  GPLv3.
  

  • [DH] Changelog
  • [DH] configure
  • [DH] doc/decoders.texi
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/allcodecs.c
  • [DH] libavcodec/avcodec.h
  • [DH] libavcodec/codec_desc.c
  • [DH] libavcodec/libaribb24.c
  • [DH] libavcodec/profiles.c
  • [DH] libavcodec/profiles.h
  • [DH] libavcodec/version.h